The term "Ah" found on acid-based batteries refers to amp hours. Amp hours is a form of measurement used to describe how much energy a specific battery can hold.
The amp hours describe the available capacity on a lead acid battery. The equation is broken down with the number before the Ah being divided by the hours printed on the battery. This yields the approximate power capacity the battery is able to maintain until it drains its power.
If a battery is labeled at 100 Ah at 1 Hr it does not mean the battery will be able to maintain 100 amps consistently at 1 hour. Lead-based acid batteries tend to decrease in capacity as the discharge rate increases.